The present invention relates generally to wireless devices and, more particularly, to powering wireless devices in a wireless field device network.
Wireless devices are becoming prevalent in industrial applications. As components of wireless field device networks, wireless devices extend the reach of control or process monitoring systems beyond that of wired devices to locations where wiring may be difficult and expensive to provide. A wireless field device network includes a cloud of wireless devices or nodes with a central controller or gateway. The nodes in the wireless network are able to both send and receive information.
Wireless field device networks are used to control and monitor disparate processes and environments. For example, wireless field device networks may be used in oil fields. An oil field is composed of numerous discrete locations centered on well pads that are scattered over large areas. Communication between these isolated local areas is essential to the overall management of the field. The wireless field device network at a well pad monitors and controls everything from flow rates, well pressure, and fluid temperature to valve status and position and potential leaks. The resulting data is relayed through the network to controllers that analyze the data and actuate control mechanisms in order to manage production or prevent trouble.
A wireless field device network is a communication network made up of a plurality of wireless devices (i.e., nodes) organized in a wireless topology. Example of wireless topologies include mesh networks, such as, for example, WIRELESSHART® networks, and star networks such as, for example, BLUETOOTH® networks. In a wireless field device network, a wireless device is one of a wireless transceiver, a wireless data router, and a wireless field device. A wireless transceiver includes a transceiver and an antenna integrated into a single device. A wireless data router includes a wireless transceiver and a data router integrated into a single device. A wireless field device includes a wireless data router and a field device integrated into a single device. A field device is a field-mounted device that performs a function in a control or process monitoring system or plant monitoring system, including all devices used in the measurement, control and monitoring of industrial plants, processes or process equipment, including plant environmental, health and safety devices. A field device typically includes at least one transducer, such as, for example, a sensor or an actuator, and may perform a control or alert function. A wireless transceiver is a device for transmitting and receiving RF-based communication data. A data router is a device that routes data packets received by a wireless transceiver, unpacking the communication payload for consumption by an attached field device (if that device's address matches the final destination address in the packet) or redirecting the communication payload back to the wireless transceiver to be relayed back into the network to the next destination in the logical path. For example, in a wireless mesh network, because each wireless device must be capable of routing messages for itself as well as other devices in the network, each wireless device includes a data router. In contrast, in a simple star network, where wireless devices need only to send and receive messages, wireless devices need not include a data router.
The use of lower power RF radios is essential for wireless network systems designed for transducer-based applications, such as a wireless field device network. Many devices in the network must be locally-powered because power utilities, such as 120V AC utilities or powered data buses, are not located nearby or are not allowed into hazardous locations where instrumentation and transducers must be located without incurring great installation expense. “Locally-powered” means powered by a local power source, such as a portable electrochemical source (e.g., long-life batteries or fuel cells) or by a low-power energy-scavenging power source (e.g., vibration, solar, or thermoelectric). A common characteristic of local power sources is their limited power capacity, either stored, as in the case of a long-life battery, or produced, as in the case of a solar panel. Batteries are expected to last more than five years and preferably last as long as the life of the product.